Automotive fog lamps are auxiliary forward lighting devices mounted in the front fascia of an automobile. Fog lamps direct light low and toward the ground to provide improved visibility during poor weather conditions. Typical “projector” automotive fog lamps include a halogen light bulb surrounded by a polyellipsoidal reflector, which is covered by a glass aspheric condenser lens. Light produced by the bulb is directed by the reflector through the lens and focused outward, typically toward the roadway.
In certain circumstances, the condenser lens of a typical fog lamp may reflect and concentrate incoming solar light rays. In particular, solar light rays incoming from certain angles may be reflected off of the back surface of the lens due to a phenomenon known as total internal reflection. The reflected solar light rays may be concentrated at a particular focal point outside of the condenser lens. For certain vehicle and fog-lamp combinations, the focal point may be located on or near the vehicle fascia or other part of the vehicle. In those vehicles, the vehicle fascia, which is typically constructed of plastic, may melt or otherwise be damaged due to excessive solar heating. Redesigning the vehicle fascia to reduce solar effects associated with fog lamps may be expensive or impossible.